A federal judge wrongly threw out a government finding that major irrigation projects in California jeopardize a threatened fish, according to an appeals court ruling.

In 2008, the U.S. Fish and Wildlife Service found that the Central Valley Project and State Water Project threaten the continued existence of delta smelt.

As part of this “biological opinion,” the agency proposed reducing the amount of water delivered though the systems from northern California to irrigators in the central and southern portions of the state.

The U.S. Bureau of Reclamation vowed to abide by these measures, but in 2010, Senior District Judge Oliver Wanger invalidated the biological opinion because it ignored the best available science.

The 9th U.S. Circuit Court of Appeals has now overturned that portion of Wanger’s ruling, finding that the “jeopardy” finding was “adequately supported by the record.”

While Wanger was “deeply critical of the biological opinion,” the 9th Circuit found that he essentially held the government to an excessively high standard.

Federal scientists aren’t required to support their conclusion that the fish are jeopardized with “anything approaching scientific certainty,” the ruling said, citing a legal precedent.

Wanger found fault with the Fish and Wildlife Service’s analysis on multiple fronts, including how smelt mortality and survival are gauged and how water salinity levels are measured.

He also said the biological opinion didn’t sufficiently back up assertions that the irrigation projects pollute the water, limit food supply for smelt and otherwise indirectly hurt the fish.

The 9th Circuit overruled these conclusions and found it was within the Fish and Wildlife Service’s to err on the side of protecting smelt.

“Facing great measurement uncertainty and a smelt population whose existence is threatened, the FWS chose to be conservative” in its water delivery recommendations, the ruling said.

The ruling won’t have immediate impacts for California farmers, who are already facing drought this year, said Damien Schiff, attorney with the Pacific Legal Foundation who represented several growers in the case.

Although Wanger overturned the biological opinion, he left in place the agency’s water restrictions, said Schiff.

However, the judge’s ruling did allow irrigators to ask the court for relief in emergency situation — an option they no longer have, he said.

“It makes their position that much more tenuous,” Schiff said.

Aside from reducing farmers’ “leverage” in irrigation decisions, the 9th Circuit ruling also demonstrates the “perniciousness” of a 1978 Supreme Court decision that makes endangered species a top federal priority, Schiff said.

“Basically, the courts are giving the Fish and Wildlife Service a blank check to divide the water up however it likes without judicial oversight,” he said. “That is very dangerous.”